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WO2015186568A1 - Nonaqueous electrolyte solution and electricity storage device using same - Google Patents

Nonaqueous electrolyte solution and electricity storage device using same Download PDF

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Publication number
WO2015186568A1
WO2015186568A1 PCT/JP2015/065088 JP2015065088W WO2015186568A1 WO 2015186568 A1 WO2015186568 A1 WO 2015186568A1 JP 2015065088 W JP2015065088 W JP 2015065088W WO 2015186568 A1 WO2015186568 A1 WO 2015186568A1
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lithium
aqueous electrolyte
carbonate
battery
electrolytic solution
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PCT/JP2015/065088
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French (fr)
Japanese (ja)
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永倉　直人
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株式会社トクヤマ
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Priority claimed from JP2014226602A external-priority patent/JP2017134888A/en
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Publication of WO2015186568A1 publication Critical patent/WO2015186568A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/04—Hybrid capacitors
    • H01G11/06—Hybrid capacitors with one of the electrodes allowing ions to be reversibly doped thereinto, e.g. lithium ion capacitors [LIC]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/54—Electrolytes
    • H01G11/58—Liquid electrolytes
    • H01G11/62—Liquid electrolytes characterised by the solute, e.g. salts, anions or cations therein
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M6/00—Primary cells; Manufacture thereof
    • H01M6/14—Cells with non-aqueous electrolyte
    • H01M6/16—Cells with non-aqueous electrolyte with organic electrolyte
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a non-aqueous electrolyte and an electricity storage device using the non-aqueous electrolyte.
  • a low-viscosity organic solvent such as a mixed solvent of ethylene carbonate and ethyl methyl carbonate
  • most low-viscosity organic solvents are vapors.
  • an electrolytic solution in which a lithium salt is dissolved in a nonaqueous solvent is used as an electrolytic solution used in an electricity storage device such as the secondary battery.
  • a nonaqueous solvent for example, a mixed solvent such as ethylene carbonate, propylene carbonate, and diethyl carbonate is generally used. LiPF 6 , LiBF 4 or the like is used as the lithium salt.
  • a negative electrode active material of a lithium ion secondary battery a carbonaceous material capable of inserting and extracting lithium ions, and a metal or alloy-based material using silicon or tin etc. aiming at high capacity, etc.
  • carbonaceous materials such as natural graphite, artificial graphite, and amorphous carbon are mainly used.
  • a transition metal composite oxide capable of inserting and extracting lithium ions is used. Typical examples of transition metals are cobalt, nickel, manganese, iron and the like.
  • Such a lithium ion secondary battery uses a highly active positive electrode and negative electrode, and it is known that the charge / discharge capacity decreases due to a side reaction between the electrode and the electrolyte, improving battery characteristics. Therefore, various studies have been made on nonaqueous solvents and electrolytes that are constituent elements of the electrolytic solution.
  • the compounds used as the electrolyte are mainly LiPF 6 and LiBF 4 .
  • LiPF 6 is preferably used.
  • Li bistrifluoromethyl sulfonic acid imide TFSI
  • Li bisfluoro sulfonic acid imide FSI
  • LiClO 4 lithium bis [pentafluoroethanesulfonyl] imide, lithium [trifluoromethanesulfonyl] [nonafluorobutanesulfonyl] imide
  • Lithium salts such as lithium tris [pentafluoroethyl] trifluorophosphate are also being studied.
  • An electrolyte solution containing an ionic compound represented by Mn + ([B (CN) 4 ⁇ m Y m ] ⁇ ) n is also known (Mn may be Li.
  • M, Y and n are Patent Documents 1 to 3).
  • lithium salt compounds specifically shown in Examples of Patent Documents 1 to 3 are lithium cyano (fluoro) oxalyl borate, lithium dicyanooxalyl borate, lithium Only tricyanomethoxyborate and lithium tricyanoethoxyborate.
  • LiPF 6 conventionally used as an electrolyte salt is extremely susceptible to hydrolysis and is a compound having poor thermal stability, and is known to decompose at 60 ° C. or higher.
  • various additives are added to increase the decomposition start temperature, and the decomposition start temperature in the electrolyte is improved to 150 ° C or higher, but this compound is fundamentally anxious. Since it is qualitative and reduces the useful life and performance of lithium batteries, it is difficult to use under extreme conditions such as high temperatures.
  • lithium salts have electrochemical stability, solubility in solvents, ionic conductivity, purity, corrosiveness to current collectors, and price problems, and those that exceed the above LiPF 6 and LiBF 4 appear Not done.
  • lithium cyano (fluoro) oxalyl borate, lithium dicyano oxalyl borate, lithium tricyanomethoxy borate and lithium tricyanoethoxy borate are considered to be compounds having a C ⁇ O bond or an alkoxy group. There is room for improvement in that the electrical conductivity when dissolved in an organic solvent is not large.
  • the present inventors have made extensive studies, and in a non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a non-aqueous solvent, a chain carbonate, a cyclic carbonate, a chain ester, a lactone and an ether are used.
  • the inventors have found that the above problems can be solved by containing one or more specific cyanofluoroborate / lithium salts in a non-aqueous solvent containing at least one selected, and completed the present invention.
  • the present invention relates to the following [1] to [7], for example.
  • An electricity storage device comprising the positive electrode, the negative electrode, and the nonaqueous electrolytic solution according to any one of [1] to [5].
  • the electricity storage device which is a lithium battery, a lithium ion battery, or a lithium ion capacitor.
  • a nonaqueous electrolytic solution capable of improving stability at high temperature and conductivity at low temperature, and an electricity storage device using the same. Specifically, by dissolving a predetermined amount of cyanofluoroborate salt in a specific non-aqueous organic solvent, it has the same electrical conductivity at room temperature as that of a known electrolytic solution, and it has high conductivity at low temperatures, and thermal decomposition. An electrolyte having a high temperature and a wide operating temperature range can be obtained.
  • lithium batteries and lithium batteries that are suitably used as non-aqueous electrolytes for on-vehicle energy storage devices or non-aqueous electrolytes for large-sized batteries for storing natural energy, are less susceptible to deterioration in electrochemical properties at high temperatures, and operate in low-temperature environments.
  • An electric storage device such as an ion battery or a lithium ion capacitor can be obtained.
  • Non-aqueous electrolyte In the nonaqueous electrolytic solution of the present invention, a lithium salt described below as an electrolyte salt is dissolved in a nonaqueous solvent.
  • the nonaqueous electrolytic solution of the present invention contains, as an electrolyte salt, a lithium salt containing at least one cyanofluoroborate / lithium salt represented by the following general formula (I) (hereinafter also referred to as lithium salt (I)). .
  • Li ⁇ BF X (CN) 4-X (I) In the above formula, X is an integer of 1 to 3. That is, Li ⁇ BF (CN) 3 , Li ⁇ BF 2 (CN) 2 and Li ⁇ BF 3 (CN) are used as the lithium salt (I) in the present invention.
  • X is 0, that is, Li ⁇ B (CN) 4 has problems of insufficient electrochemical stability and low electrical conductivity at low temperatures.
  • LiBF 4 has a problem of low electrical conductivity.
  • a compound substituted with another group instead of the fluorine atom (F) has problems of low electrochemical stability and low electrical conductivity.
  • the lithium salt (I) has an effect of sufficient electrochemical stability and high electrical conductivity particularly at a low temperature because the boron atom is substituted with both a fluorine atom and a cyano group.
  • the thermal decomposition temperature of the lithium salt (I) is 160 ° C. or higher, and all three can be suitably used. Among them, Li ⁇ BF 2 (CN) 2 and Li ⁇ BF (CN) 3 have decomposition temperatures. Since it is 180 degreeC or more, it is more suitable. Specifically, the thermal decomposition temperature of Li ⁇ BF 2 (CN) 2 was 190 ° C., and the thermal decomposition temperature of Li ⁇ BF (CN) 3 was 240 ° C. (this thermal decomposition temperature is shown in the examples below).
  • Li ⁇ BF 2 (CN) 2 has a high decomposition temperature, and in addition, the conductivity when dissolved in an organic solvent is the conductivity when other cyanofluoroborate salts are dissolved at the same concentration. It is particularly suitable because it is higher and has sufficient oxidation resistance.
  • Li ⁇ BF 2 (CN) 2 and Li ⁇ BF (CN) 3 are also stable against water.
  • the lithium salt used in the non-aqueous electrolyte of the present invention may be mixed with the above-mentioned lithium salt (I) and other lithium salts.
  • the other lithium salt existing lithium other than the lithium salt (I) may be used.
  • a salt can be used without particular limitation.
  • lithium salts include CF 3 SO 3 Li, LiN (FSO 2 ) 2 , LiN (FSO 2 ) (CF 3 SO 2 ), LiN (CF 3 SO 2 ) 2 , LiN (C 2 F 5 SO 2 ). 2 , lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropane disulfonylimide, LiC (FSO 2 ) 3 , LiC (CF 3 SO 2 ) 3 , LiC (C 2 F 5 SO 2 ) 3 , lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium tetrafluorooxalate phosphate, lithium difluorobisoxalatophosphate, LiBF 3 CF 3 , LiBF 3 C 2 F 5 , LiPF 3 (CF 3 ) 3 , organic lithium salts such as LiPF 3 (C 2 F 5 ) 3, and LiPF 6 , LiBF 4 , Li
  • the other lithium salts may be used alone or in combination of two or more.
  • the blending ratio of these other lithium salts is preferably less than 50 mol%, more preferably 30 mol% or less in the total lithium salt.
  • the total lithium salt is the total of lithium salts contained in the non-aqueous electrolyte, that is, the total of the lithium salt (I) and other lithium salts.
  • the other lithium salt is blended, depending on the salt to be blended, the viscosity of the non-aqueous electrolyte increases and the electrical conductivity decreases, or the electrochemical stability and high-temperature stability of the non-aqueous electrolyte decrease. There is a fear. Therefore, an embodiment in which no other lithium salt is contained is preferable.
  • the content of all lithium salts contained in the nonaqueous electrolytic solution is preferably 0.3 to 4 mol / L, and usually 0.3 mol / L in the nonaqueous electrolytic solution.
  • it is 0.5 mol / L or more, More preferably, it is 0.7 mol / L or more, Usually, 4 mol / L or less, More preferably, it is 3 mol / L or less, More preferably, it is 1.5 mol / L or less. If it is this density
  • the content of the lithium salt (I) in the non-aqueous electrolyte is preferably 0.3 to 4 mol / L, more preferably 0.5 to 3 mol / L, and still more preferably 0.7 to 1.5 mol. / L.
  • the lithium salt (I) can be synthesized by a known method.
  • a lithium metal cyanide compound is dissolved in an organic solvent such as acetonitrile and acetone, and BF 3 gas is blown, or a lithium metal
  • a cyanide compound is reacted with a BF 3 addition compound such as boron trifluoride ether BF 3 ⁇ OEt 2 in the presence of an aprotic solvent such as acetonitrile, diethyl ether, tetrahydrofuran and dimethoxyethane.
  • potassium, sodium, such as magnesium and calcium, cyanide of an alkali metal or alkaline earth metal other than lithium the above BF 3 gas in the resulting solution is dissolved in an organic solvent BF 3 adduct such as boron trifluoride ether BF 3 ⁇ OEt 2 is allowed to act in the presence of an aprotic solvent to synthesize a corresponding alkali metal or alkaline earth metal salt of cyanofluoroborate,
  • the synthesized lithium salt (I) when used for the non-aqueous electrolyte of the present invention, it is preferable to sufficiently remove impurities by, for example, sufficiently washing with water and drying.
  • the metal concentration other than Li is 1000 ppm or less, Na is 20 ppm or less, K is 10 ppm or less, Ca is 10 ppm or less, Fe is 3 ppm or less, and Pb is 10 ppm or less.
  • Preferable (both lithium salt (I) is 100% by mass).
  • Nonaqueous solvent Battery electrolytes are required to have 1) electrochemical stability in the range of use, 2) high solubility in electrolyte salts, and 3) high electrical conductivity due to low viscosity.
  • lithium ion batteries have a charge / discharge potential of about 0 to 4.5 V vs. Li + / Li, which is very wide compared to other batteries, and the solvents that can be used are limited.
  • the organic solvent (nonaqueous solvent) used in the nonaqueous electrolytic solution of the present invention contains at least one selected from the group consisting of a chain carbonate, a cyclic carbonate, a chain ester, a lactone and an ether. This non-aqueous solvent does not contain water.
  • Examples of the organic solvent that can be used in the present invention include the following organic solvents (non-aqueous solvents).
  • chain carbonate a chain carbonate having 3 to 6 carbon atoms is preferable.
  • Specific examples of the chain carbonate include dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.
  • cyclic carbonate a cyclic carbonate having 3 to 6 carbon atoms is preferable.
  • Specific examples of the cyclic carbonate include ethylene carbonate and propylene carbonate.
  • the chain ester is preferably a chain ester having 3 to 6 carbon atoms.
  • Specific examples of the chain ester include ethyl propionate, methyl propionate, ethyl acetate, and methyl acetate.
  • lactones examples include lactones having 3 to 6 carbon atoms.
  • Specific examples of the lactone include ⁇ -butyrolactone.
  • the ether is preferably an ether having 3 to 8 carbon atoms.
  • Specific ethers include dimethoxyethane, ethoxymethoxyethane, diethoxyethane, and triethylene glycol dimethyl ether.
  • organic solvents nonaqueous solvents
  • those that are solid when the electrolytic solution is prepared or used are mixed with the above-mentioned other organic solvents (nonaqueous solvents) that are liquid. It can be used as a mixed solvent.
  • Organic solvents other than the above are usually unsuitable as electrolytes because of insufficient electrochemical stability, low solubility of electrolyte salts, high viscosity and low electrical conductivity.
  • the above solvents may be used alone or in combination of two or more.
  • a high dielectric constant solvent such as cyclic carbonates
  • a low viscosity solvent such as chain carbonates and chain esters.
  • a chain carbonate or a cyclic carbonate should be used as a non-aqueous solvent.
  • a mixed solvent of a chain carbonate and a cyclic carbonate it is preferable to use.
  • the viscosity of the electrolytic solution can be easily adjusted and the electrical conductivity can be increased when the linear carbonate content in the mixed solvent is 15% or more by volume% (23 ° C.). Therefore, it is suitable.
  • the chain carbonate content is 90% or less in terms of volume% (23 ° C.)
  • a decrease in electrical conductivity due to a decrease in the dielectric constant of the solvent can be reduced.
  • the chain carbonate content is preferably 15% to 90%
  • the cyclic carbonate content is preferably 10% to 85%
  • the chain carbonate content is 20% to 85%.
  • the cyclic carbonate content is 15% to 80%, the chain carbonate content is 25% to 80%, and the cyclic carbonate content is 20% to 75%. Preferred (however, the total volume% of the chain carbonate and cyclic carbonate at 23 ° C. is 100%).
  • the chain carbonate content is 40% or more and 85% or less, and the ethylene carbonate content is 15% or more and 60%.
  • the chain carbonate content is preferably 45% or more and 80% or less, and the ethylene carbonate content is more preferably 20% or more and 55% or less.
  • the non-aqueous electrolyte of the present invention may also contain an additive used for an existing battery or an electric double layer capacitor electrolyte.
  • the electrolyte for a lithium ion battery contains various additives for the purpose of flame retardancy and cycle characteristics improvement, but the existing additive can be used as it is for the non-aqueous electrolyte.
  • the additive include unsaturated carbonates containing double bonds and fluorinated carbonates.
  • the unsaturated carbonate containing a double bond include vinylene carbonate and vinyl ethylene carbonate.
  • the fluorinated carbonate include a fluorinated dimethyl carbonate derivative and a fluorinated ethyl methyl carbonate derivative. And fluorinated diethyl carbonate derivatives.
  • the mainstream hexafluorophosphate lithium salt starts to decompose at around 60 ° C. and is essentially unstable to water, and is a sensitive compound that decomposes by reacting with moisture. It is.
  • a lithium ion battery or the like reacts with a solvent or the like at the time of charging, and moisture can easily be generated by the reaction. Therefore, even if the reaction is suppressed by an additive or the like, the deterioration of the electrolyte salt is considered to proceed essentially.
  • the thermal decomposition temperature of the lithium salt (I) used in the present invention is 160 ° C or higher
  • the thermal decomposition temperature of a suitable compound is 180 ° C or higher
  • the thermal decomposition temperature of a more preferable compound is 200 ° C or higher.
  • This thermal decomposition temperature is a value measured by the method described in the Examples below). Therefore, it is considered stable at high temperatures because of the inherent stability of the compounds.
  • the non-aqueous electrolyte of the present invention exhibits high conductivity, particularly high ion conductivity even at low temperatures, is not necessarily clear, but the ion diameter of the anion of the lithium salt (I) that is an electrolyte salt and This is because the molecular weight is relatively small, especially with respect to the ion diameter and molecular weight of the hexafluorophosphate anion, and because the symmetry is small, it is difficult to precipitate and the polarity of the anion is small and the interaction between compounds is small. It is believed that there is.
  • the non-aqueous electrolyte can be used for power storage devices such as lithium batteries (lithium primary batteries), lithium ion batteries (lithium secondary batteries), and lithium ion capacitors. Among these, it is more preferable to use as a lithium battery and a lithium ion battery, and it is most preferable to use as a lithium ion battery. Further, the nonaqueous electrolytic solution may be used in a gel form as well as in a liquid form. Furthermore, the non-aqueous electrolyte of the present invention can be used for a solid polymer electrolyte.
  • the electricity storage device of the present invention uses lithium salt (I) as a non-aqueous electrolyte, so that it has little deterioration even when stored at a high temperature of 60 ° C. or higher, and has an electrical conductivity higher than that of an existing electrolyte from room temperature to low temperature. It can be made into an electrolyte that is electrochemically stable.
  • the lithium battery includes a negative electrode, a positive electrode, a separator disposed between the positive electrode and the negative electrode, and the nonaqueous electrolytic solution of the present invention.
  • the lithium battery has the same configuration as the known lithium battery except for the non-aqueous electrolyte.
  • the positive electrode and the negative electrode are laminated through a porous film impregnated with the non-aqueous electrolyte, and these are the cases. It has the form stored in. Therefore, the shape of the lithium battery is not particularly limited, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.
  • At least one selected from the group consisting of lithium and lithium alloys is used as an active material.
  • the positive electrode contains a positive electrode active material, and preferably further contains a conductive material and a binder.
  • a positive electrode active material materials commonly used in the field of lithium batteries can be used as they are, and among them, metal oxides such as manganese dioxide, graphite fluoride, thionyl chloride and the like can be preferably used.
  • Manganese dioxide is particularly preferable because of its good discharge characteristics.
  • the non-aqueous electrolyte of the present invention using a lithium salt (I) is a battery that can be discharged at a current higher than that of an existing lithium battery from room temperature to low temperature with little deterioration even when stored at a high temperature of 60 ° C. or higher. Can do.
  • ⁇ Lithium ion battery> The lithium ion battery includes a negative electrode and a positive electrode that can occlude and release lithium ions, a separator disposed between the positive electrode and the negative electrode, and the nonaqueous electrolytic solution of the present invention.
  • the lithium ion battery is the same as the known lithium ion battery in terms of the configuration other than the non-aqueous electrolyte, and usually the positive electrode and the negative electrode are laminated through the porous film impregnated with the non-aqueous electrolyte, These have the form accommodated in the case. Therefore, the shape of the lithium ion battery is not particularly limited, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.
  • a negative electrode used for a lithium ion battery has a negative electrode active material layer on a current collector.
  • the negative electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. Specific examples thereof include carbonaceous materials, alloy-based materials, lithium-containing metal composite oxide materials, and the like. These may be used individually by 1 type, and may be used together combining 2 or more types arbitrarily.
  • the positive electrode active material is preferably a material containing lithium and at least one transition metal. Specific examples include lithium transition metal composite oxides and lithium-containing transition metal phosphate compounds. These positive electrode active materials may be used alone or in any combination of two or more.
  • Lithium ion batteries have excellent electrochemical characteristics at high temperatures even when the end-of-charge voltage is 4.2 V or higher, particularly 4.3 V or higher.
  • the lithium ion battery according to the present invention can be charged and discharged at ⁇ 40 to 100 ° C.
  • the non-aqueous electrolyte of the present invention using a lithium salt (I) is a secondary that can be charged and discharged at a current higher than that of an existing lithium ion battery from room temperature to low temperature even when stored at a high temperature of 60 ° C. or higher. It can be a battery.
  • a lithium ion capacitor is a power storage device that uses a carbon material such as graphite as a negative electrode and stores energy using lithium ion intercalation thereto.
  • the positive electrode include those using an electric double layer between an activated carbon electrode and an electrolytic solution, those using a ⁇ -conjugated polymer electrode doping / dedoping reaction, and the like.
  • LIC Since the above-described electrolytic solution is used as the electrolytic solution, LIC can achieve both electrochemical stability at high temperature and high conductivity at low temperature.
  • Example 1-1 25 ml of diethyl carbonate was added to 33 g of ethylene carbonate and dissolved, and 5.39 g of Li ⁇ BF 2 (CN) 2 was added and stirred to dissolve completely. 1: 1 (23 ° C. volume ratio) of ethylene carbonate and diethyl carbonate ) A non-aqueous electrolyte solution in which Li ⁇ BF 2 (CN) 2 was dissolved in a mixed solvent at a concentration of 1 mol / L was prepared.
  • the electrical conductivity and electrochemical stability at 23 ° C., 0 ° C. and ⁇ 10 ° C. of the obtained nonaqueous electrolytic solution were measured.
  • the measurement results are shown in Table 1.
  • the measurement result of the cyclic voltammogram of the non-aqueous electrolyte is shown in FIG.
  • Example 1-2 Except for using 5.74 g of Li ⁇ BF (CN) 3, the mixture was mixed with a mixed solvent of ethylene carbonate and diethyl carbonate in a 1: 1 (23 ° C. volume ratio) mixed solvent of Li ⁇ BF (CN). ) A nonaqueous electrolytic solution in which 3 was dissolved at a concentration of 1 mol / L was prepared.
  • the electrical conductivity and electrochemical stability at 23 ° C., 0 ° C. and ⁇ 10 ° C. of the obtained non-aqueous electrolyte were measured.
  • the measurement results are shown in Table 1.
  • the measurement result of the cyclic voltammogram of the non-aqueous electrolyte is shown in FIG.
  • the nonaqueous electrolytic solution using the cyanofluoroborate / lithium salt of the present invention has an electrical conductivity even at a low temperature as compared with the conventional nonaqueous electrolytic solution using LiPF 6 or LiBF 4 as the electrolyte salt. Is suitable for use at low temperatures.
  • the non-aqueous electrolyte of the present invention has the same electrical conductivity and electrochemical stability at room temperature as the conventional non-aqueous electrolyte, and the electrolyte salt has a relatively high thermal decomposition temperature, so that the operating temperature range is wide. It can be suitably used as a lithium ion battery electrolyte or a lithium ion capacitor electrolyte.
  • Example 2-1 Comparison of electrical conductivity depending on the solvent of non-aqueous electrolyte
  • GBL ⁇ -butyrolactone
  • Example 2-2 to 2-15 A non-aqueous electrolyte was prepared in the same manner as in Example 2-1, except that the type and concentration of the lithium salt and the type of the non-aqueous solvent were changed as described in Table 2 or 3. The electrical conductivity of was measured. The results are shown in Table 2 or 3. Li ⁇ BF 2 (CN) 2 is 0.52 g when the concentration of the electrolytic solution is 0.5 mol / L, 1.04 g when the concentration is 1.0 mol / L, and 2 when the concentration is 2.0 mol / L. 0.08 g was used, and Li ⁇ BF (CN) 3 was used at 0.58 g when the concentration of the electrolytic solution was 0.5 mol / L and 1.15 g when 1.0 mol / L was used.
  • Li ⁇ BF 2 (CN) 2 and Li ⁇ BF (CN) 3 which are cyanofluoroborate / lithium salts, are used for organic solvents such as lactones, ethers, chain carbonates and cyclic carbonates. It dissolves in a wide concentration and shows high electrical conductivity. Therefore, it can be suitably used as an electrolyte for lithium ion batteries or an electrolyte for lithium ion capacitors.
  • Example 3 In the positive electrode, 93 parts of LiNi 1/3 Co 1/3 Mn 1/3 O 2 as an active material, 4 parts of acetylene black as a conductive material, and 3 parts of polyvinylidene fluoride as a binder were slurried into a current collector foil. It was coated with an applicator, dried at 120 ° C. for 10 minutes and then pressed.
  • the negative electrode was prepared in the same process as the positive electrode, using 93 parts of graphite as an active material, 2 parts of acetylene black as a conductive material, and 5 parts of polyvinylidene fluoride as a binder.
  • the electrolytic solution used was a solvent obtained by mixing ethylene carbonate and diethyl carbonate in a volume ratio of 1: 1 at 23 ° C. as a solvent, and Li ⁇ BF 2 (CN) dried at 70 ° C. for 12 hours under reduced pressure.
  • 2 1M (1 defined, 1 mol / L) under an argon atmosphere using a solution such that.
  • the separator used was a polyethylene microporous membrane (thickness 20 ⁇ m, porosity 40%).
  • the positive electrode and negative electrode prepared above were punched out to 30 ⁇ 50 mm 2 and dried at 170 ° C. for 10 hours, respectively, opposed to each other through a separator, inserted into an aluminum laminate, injected with an electrolytic solution, impregnated under reduced pressure, and then vacuumed A single-layer laminate cell (battery) for battery performance evaluation was produced by sealing.
  • the battery produced in Example 3 has a small increase in resistance compared with the battery produced in Comparative Example 3 after high temperature storage (85 ° C., 10 days). It was found to be stable.
  • the battery produced in Example 3 has a higher discharge capacity and lower resistance at a lower temperature than the battery produced in Comparative Example 3, and thus has superior battery performance at low temperatures. I understood that.

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Abstract

Provided are: a nonaqueous electrolyte solution having both stability at high temperatures and high conductivity at low temperatures; and an electricity storage device comprising this nonaqueous electrolyte solution. A nonaqueous electrolyte solution wherein at least one lithium salt is dissolved in a nonaqueous solvent, and which is characterized in that: the nonaqueous solvent contains at least one substance selected from the group consisting of chain carbonates, cyclic carbonates, chain esters, lactones and ethers; the lithium salt contains at least one cyanofluoroborate-lithium salt represented by general formula (I); and the total concentration of all the lithium salts contained in the nonaqueous electrolyte solution is 0.3-4 mol/L. Li·BFX(CN)4-X (I) (In the formula, X represents an integer of 1-3.)

Description

非水電解液およびそれを用いた蓄電デバイスNon-aqueous electrolyte and power storage device using the same
　本発明は、非水電解液および該非水電解液を用いた蓄電デバイスに関する。 The present invention relates to a non-aqueous electrolyte and an electricity storage device using the non-aqueous electrolyte.
　近年、携帯用電子機器、携帯電話およびビデオカメラなどが急激に普及し、それらに用いられる軽量で高性能の二次電池の需要が大幅に増大した。また、近年、二次電池は、車載用途または自然エネルギーの貯蔵用途などに向けての開発が進められている。車載用途では使用環境温度は－３０℃から６０℃が想定されており、従来使用されている温度領域より厳しい使用環境が想定され、高温側では電解質の耐久性が求められ、低温側では従来以上のイオン伝導率が求められている。特に高温環境については、セルが大型化されるため、使用環境のみならず、自己発熱によって定常的に比較的高い温度にさらされることになり、高温耐久性の向上は重要な開発課題になってきている。 In recent years, portable electronic devices, mobile phones, video cameras, and the like have spread rapidly, and the demand for lightweight, high-performance secondary batteries used for them has greatly increased. In recent years, secondary batteries have been developed for in-vehicle applications or natural energy storage applications. For automotive applications, the operating environment temperature is assumed to be -30 ° C to 60 ° C, and it is assumed that the operating environment will be harsher than the temperature range used in the past. The ionic conductivity of is required. Especially in the high temperature environment, since the cell becomes large, not only the use environment but also the self-heating will steadily be exposed to a relatively high temperature, and improving the high temperature durability has become an important development issue. ing.
　また、車載用途または自然エネルギーの貯蔵用途の電池の場合、使用条件として－３０℃での作動が想定され、低温でのイオン伝導性も要求される。低温でのイオン伝導度低下を避けるために通常は低粘度の有機溶媒(炭酸エチレンと炭酸エチルメチルとの混合溶媒など)を用いる事が行われているが、ほとんどの低粘度の有機溶媒は蒸気圧が高く、デンドライト析出などにより電池にショートが発生した場合、容易に火災が発生するなど安全性が低下する問題点がある。 In addition, in the case of a battery for in-vehicle use or storage of natural energy, operation at −30 ° C. is assumed as a use condition, and ion conductivity at low temperature is also required. In order to avoid a decrease in ionic conductivity at low temperatures, a low-viscosity organic solvent (such as a mixed solvent of ethylene carbonate and ethyl methyl carbonate) is usually used, but most low-viscosity organic solvents are vapors. When the pressure is high and a short circuit occurs in the battery due to dendrite deposition, there is a problem that the safety is lowered, for example, fire is easily generated.
　前記二次電池等の蓄電デバイスに用いられている電解液として、多くの場合、非水溶媒にリチウム塩を溶解した電解液が使用されている。さらに、非水溶媒としては、例えば炭酸エチレン、炭酸プロピレン、炭酸ジエチル等の混合溶媒が一般的に使用されている。リチウム塩としてはＬｉＰＦ6、ＬｉＢＦ4などが用いられている。 In many cases, an electrolytic solution in which a lithium salt is dissolved in a nonaqueous solvent is used as an electrolytic solution used in an electricity storage device such as the secondary battery. Furthermore, as the non-aqueous solvent, for example, a mixed solvent such as ethylene carbonate, propylene carbonate, and diethyl carbonate is generally used. LiPF 6 , LiBF 4 or the like is used as the lithium salt.
　また、リチウムイオン二次電池の負極活物質としては、リチウムイオンを吸蔵および放出することができる炭素質材料、ならびに、高容量化を目指してシリコンまたはスズ等を用いた金属または合金系の材料などが知られ、現在は炭素質材料である天然黒鉛、人造黒鉛、非晶質炭素等が主に用いられている。正極活物質としてはリチウムイオンを吸蔵および放出することができる遷移金属複合酸化物が用いられている。遷移金属の代表例としてはコバルト、ニッケル、マンガン、鉄等である。 In addition, as a negative electrode active material of a lithium ion secondary battery, a carbonaceous material capable of inserting and extracting lithium ions, and a metal or alloy-based material using silicon or tin etc. aiming at high capacity, etc. Currently, carbonaceous materials such as natural graphite, artificial graphite, and amorphous carbon are mainly used. As the positive electrode active material, a transition metal composite oxide capable of inserting and extracting lithium ions is used. Typical examples of transition metals are cobalt, nickel, manganese, iron and the like.
　このようなリチウムイオン二次電池は、活性の高い正極と負極とを使用しているため、電極と電解液との副反応により充放電容量が低下することが知られており、電池特性を改良するために、電解液の構成要素である非水溶媒および電解質について種々の検討がなされている。 Such a lithium ion secondary battery uses a highly active positive electrode and negative electrode, and it is known that the charge / discharge capacity decreases due to a side reaction between the electrode and the electrolyte, improving battery characteristics. Therefore, various studies have been made on nonaqueous solvents and electrolytes that are constituent elements of the electrolytic solution.
　電解質として用いられている化合物は主にＬｉＰＦ6およびＬｉＢＦ4である。このうちＬｉＢＦ4は有機溶媒に溶解性が低く伝導度の面で良好でないため、ＬｉＰＦ6が好適に用いられている。 The compounds used as the electrolyte are mainly LiPF 6 and LiBF 4 . Among Since LiBF 4 is not good in terms of low conductivity soluble in organic solvent, LiPF 6 is preferably used.
　その他に、Ｌｉビストリフルオロメチルスルフォン酸イミド（ＴＦＳＩ）、Ｌｉビスフルオロスルフォン酸イミド（ＦＳＩ）、ＬｉＣｌＯ4、リチウムビス［ペンタフルオロエタンスルホニル］イミド、リチウム［トリフルオロメタンスルホニル］［ノナフルオロブタンスルホニル］イミド、リチウムシクロヘキサフルオロプロパン－１，３－ビス［スルホニル］イミド、リチウムビス［オキサレート（２－）］ボレート、リチウムトリフルオロメチルトリフルオロボレート、リチウムペンタフルオロエチルトリフルオロボレート、リチウムヘプタフルオロプロピルトリフルオロボレート、リチウムトリス［ペンタフルオロエチル］トリフルオロホスフェートなどのリチウム塩も検討されている。 In addition, Li bistrifluoromethyl sulfonic acid imide (TFSI), Li bisfluoro sulfonic acid imide (FSI), LiClO 4 , lithium bis [pentafluoroethanesulfonyl] imide, lithium [trifluoromethanesulfonyl] [nonafluorobutanesulfonyl] imide Lithium cyclohexafluoropropane-1,3-bis [sulfonyl] imide, lithium bis [oxalate (2-)] borate, lithium trifluoromethyl trifluoroborate, lithium pentafluoroethyl trifluoroborate, lithium heptafluoropropyl trifluoroborate Lithium salts such as lithium tris [pentafluoroethyl] trifluorophosphate are also being studied.
　また、Ｍｎ+（[Ｂ（ＣＮ）4-mＹm]-）nで示されるイオン性化合物を含む電解質液も知られている（ＭｎはＬｉであってもよい。ｍ、Ｙおよびｎは、特許文献１～３参照）。上記式で規定した化合物は、非常に数多く存在するが、特許文献１～３の実施例に具体的に示されたリチウム塩の化合物は、リチウムシアノ（フルオロ）オキサリルボレート、リチウムジシアノオキサリルボレート、リチウムトリシアノメトキシボレート、リチウムトリシアノエトキシボレートだけである。 An electrolyte solution containing an ionic compound represented by Mn + ([B (CN) 4−m Y m ] − ) n is also known (Mn may be Li. M, Y and n are Patent Documents 1 to 3). There are a large number of compounds defined by the above formulas, but lithium salt compounds specifically shown in Examples of Patent Documents 1 to 3 are lithium cyano (fluoro) oxalyl borate, lithium dicyanooxalyl borate, lithium Only tricyanomethoxyborate and lithium tricyanoethoxyborate.
特開２０１４－５２６１号公報JP 2014-5261 A 特開２０１３－１４９５８５号公報JP 2013-149585 A 国際公開第２０１２／０９９２５９号International Publication No. 2012/099259
　従来電解質塩として用いられているＬｉＰＦ6は、極めて加水分解を受けやすく、また、熱安定性が悪い化合物であり６０℃以上で分解することが知られている。現行の電解液ではさまざまな添加剤を付加して分解開始温度を上げることが行われており、電解液中の分解開始温度は１５０℃以上まで向上しているが、根本的にこの化合物は不安定性であり、リチウム電池の耐用年数および性能を低下させるため、高温など極端な条件で使用することは難しい。 LiPF 6 conventionally used as an electrolyte salt is extremely susceptible to hydrolysis and is a compound having poor thermal stability, and is known to decompose at 60 ° C. or higher. In current electrolytes, various additives are added to increase the decomposition start temperature, and the decomposition start temperature in the electrolyte is improved to 150 ° C or higher, but this compound is fundamentally anxious. Since it is qualitative and reduces the useful life and performance of lithium batteries, it is difficult to use under extreme conditions such as high temperatures.
　その他のリチウム塩は、電気化学安定性、溶媒に対する溶解性、イオン伝導度、純度、集電体に対する腐食性、さらには、価格の問題があり、上記のＬｉＰＦ6およびＬｉＢＦ4を超えるものは出現していない。 Other lithium salts have electrochemical stability, solubility in solvents, ionic conductivity, purity, corrosiveness to current collectors, and price problems, and those that exceed the above LiPF 6 and LiBF 4 appear Not done.
　また、リチウムシアノ（フルオロ）オキサリルボレート、リチウムジシアノオキサリルボレート、リチウムトリシアノメトキシボレートおよびリチウムトリシアノエトキシボレートは、Ｃ＝Ｏ結合またはアルコキシ基を有する化合物であるためと考えられるが、電気化学安定性と有機溶媒に溶解させたときの電気伝導度とが大きくないという点で改善の余地があった。 In addition, lithium cyano (fluoro) oxalyl borate, lithium dicyano oxalyl borate, lithium tricyanomethoxy borate and lithium tricyanoethoxy borate are considered to be compounds having a C═O bond or an alkoxy group. There is room for improvement in that the electrical conductivity when dissolved in an organic solvent is not large.
　本発明は、広い範囲で電気化学的に安定であり、高温での安定性を改善でき、特に低温での伝導度を向上できる非水電解液及びそれを用いた蓄電デバイスを提供することを課題とする。 It is an object of the present invention to provide a nonaqueous electrolytic solution that is electrochemically stable over a wide range, can improve stability at high temperatures, and can improve conductivity at low temperatures, and a power storage device using the same. And
　本発明者らは、上記課題を解決するために鋭意研究を重ね、非水溶媒に電解質塩が溶解されている非水電解液において、鎖状カーボネート、環状カーボネート、鎖状エステル、ラクトンおよびエーテルから選ばれる少なくとも１種を含む非水溶媒中に特定のシアノフルオロボレート・リチウム塩を１種以上含有することで、上記課題を解決できることを見出し、本発明を完成した。 In order to solve the above-mentioned problems, the present inventors have made extensive studies, and in a non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a non-aqueous solvent, a chain carbonate, a cyclic carbonate, a chain ester, a lactone and an ether are used. The inventors have found that the above problems can be solved by containing one or more specific cyanofluoroborate / lithium salts in a non-aqueous solvent containing at least one selected, and completed the present invention.
　すなわち、本発明は、例えば以下の［１］～［７］に関する。 That is, the present invention relates to the following [1] to [7], for example.
　[１]非水溶媒中に少なくとも１種のリチウム塩が溶解している非水電解液であって、前記非水溶媒が、鎖状カーボネート、環状カーボネート、鎖状エステル、ラクトンおよびエーテルよりなる群から選ばれる少なくとも１種を含み、前記リチウム塩が、下記一般式（Ｉ）で表されるシアノフルオロボレート・リチウム塩を少なくとも１種含み、
Ｌｉ・ＢＦX（ＣＮ）4-X　　　…（Ｉ）
（Ｘは１～３の整数である）
　非水電解液に含まれる全リチウム塩の合計の濃度が０．３～４ｍｏｌ／Ｌであることを特徴とする非水電解液。 [1] A non-aqueous electrolyte in which at least one lithium salt is dissolved in a non-aqueous solvent, wherein the non-aqueous solvent is composed of a chain carbonate, a cyclic carbonate, a chain ester, a lactone, and an ether And the lithium salt contains at least one cyanofluoroborate lithium salt represented by the following general formula (I):
Li · BF X (CN) 4 -X ... (I)
(X is an integer of 1 to 3)
A nonaqueous electrolytic solution, wherein the total concentration of all lithium salts contained in the nonaqueous electrolytic solution is 0.3 to 4 mol / L.
　[２]前記一般式（Ｉ）で表わされるシアノフルオロボレート・リチウム塩の合計の濃度が、０．３～４ｍｏｌ／Ｌであることを特徴とする[１]に記載の非水電解液。 [2] The nonaqueous electrolytic solution according to [1], wherein the total concentration of the cyanofluoroborate / lithium salt represented by the general formula (I) is 0.3 to 4 mol / L.
　[３]前記非水溶媒が、鎖状カーボネートと環状カーボネートとを含むことを特徴とする[１]または[２]に記載の非水電解液。 [3] The nonaqueous electrolytic solution according to [1] or [2], wherein the nonaqueous solvent includes a chain carbonate and a cyclic carbonate.
　[４]蓄電デバイスに用いられることを特徴とする[１]～[３]のいずれかに記載の非水電解液。 [4] The nonaqueous electrolytic solution according to any one of [1] to [3], which is used for an electricity storage device.
　[５]リチウム電池、リチウムイオン電池またはリチウムイオンキャパシタに用いられることを特徴とする[１]～[３]のいずれかに記載の非水電解液。 [5] The nonaqueous electrolytic solution according to any one of [1] to [3], which is used for a lithium battery, a lithium ion battery, or a lithium ion capacitor.
　[６]正極、負極および[１]～[５]のいずれかに記載の非水電解液を有することを特徴とする蓄電デバイス。 [6] An electricity storage device comprising the positive electrode, the negative electrode, and the nonaqueous electrolytic solution according to any one of [1] to [5].
　[７]リチウム電池、リチウムイオン電池またはリチウムイオンキャパシタであることを特徴とする[６]に記載の蓄電デバイス。 [7] The electricity storage device according to [6], which is a lithium battery, a lithium ion battery, or a lithium ion capacitor.
　本発明によれば、高温での安定性と特に低温での伝導度などとを向上できる非水電解液及びそれを用いた蓄電デバイスを提供することができる。具体的には、特定の非水系有機溶媒に所定量のシアノフルオロボレート塩を溶解させることで、公知の電解液に比べて室温で同等の電気伝導度を持ち低温では伝導度が高く、熱分解温度も高く、作動温度領域が広い電解液が得られる。特に車載用蓄電デバイス用の非水電解液または自然エネルギー貯蔵用の大型電池の非水電解液として好適に使用され、高温での電気化学特性が低下しにくく、低温環境でも動作するリチウム電池、リチウムイオン電池、またはリチウムイオンキャパシタ等の蓄電デバイスを得ることができる。 According to the present invention, it is possible to provide a nonaqueous electrolytic solution capable of improving stability at high temperature and conductivity at low temperature, and an electricity storage device using the same. Specifically, by dissolving a predetermined amount of cyanofluoroborate salt in a specific non-aqueous organic solvent, it has the same electrical conductivity at room temperature as that of a known electrolytic solution, and it has high conductivity at low temperatures, and thermal decomposition. An electrolyte having a high temperature and a wide operating temperature range can be obtained. In particular, lithium batteries and lithium batteries that are suitably used as non-aqueous electrolytes for on-vehicle energy storage devices or non-aqueous electrolytes for large-sized batteries for storing natural energy, are less susceptible to deterioration in electrochemical properties at high temperatures, and operate in low-temperature environments. An electric storage device such as an ion battery or a lithium ion capacitor can be obtained.
実施例１の電解液のサイクリックボルタモグラムの測定結果Measurement result of cyclic voltammogram of electrolyte of Example 1 実施例２の電解液のサイクリックボルタモグラムの測定結果Measurement result of cyclic voltammogram of electrolyte of Example 2 実施例７の初期充放電特性の測定結果Measurement results of initial charge / discharge characteristics of Example 7
　〔非水電解液〕
　本発明の非水電解液は、非水溶媒に電解質塩として下記で説明するリチウム塩が溶解されている。 [Non-aqueous electrolyte]
In the nonaqueous electrolytic solution of the present invention, a lithium salt described below as an electrolyte salt is dissolved in a nonaqueous solvent.
　＜リチウム塩＞
　本発明の非水電解液は、下記一般式（Ｉ）で表されるシアノフルオロボレート・リチウム塩（以下、リチウム塩（Ｉ）ともいう。）を１種以上含むリチウム塩を電解質塩として含有する。
Ｌｉ・ＢＦX（ＣＮ）4-X　　…（Ｉ）
　上記式においてＸは１から３の整数である。即ち、Ｌｉ・ＢＦ（ＣＮ）3、Ｌｉ・ＢＦ2（ＣＮ）2及びＬｉ・ＢＦ3（ＣＮ）が本発明におけるリチウム塩（Ｉ）として使用される。Ｘが０の場合、即ち、Ｌｉ・Ｂ（ＣＮ）4は電気化学安定性が十分でないことと低温での電気伝導度の低さという問題がある。一方、Ｘが４の場合、即ち、ＬｉＢＦ4は電気伝導度の低さという問題がある。またフッ素原子（Ｆ）に代えて他の基で置換された化合物では電気化学安定性の低さと電気伝導度の低さという問題がある。それに対しリチウム塩（Ｉ）は、ホウ素原子がフッ素原子およびシアノ基の双方で置換されていることにより、十分な電気化学安定性と特に低温での高電気伝導度という効果を有する。 <Lithium salt>
The nonaqueous electrolytic solution of the present invention contains, as an electrolyte salt, a lithium salt containing at least one cyanofluoroborate / lithium salt represented by the following general formula (I) (hereinafter also referred to as lithium salt (I)). .
Li · BF X (CN) 4-X (I)
In the above formula, X is an integer of 1 to 3. That is, Li · BF (CN) 3 , Li · BF 2 (CN) 2 and Li · BF 3 (CN) are used as the lithium salt (I) in the present invention. When X is 0, that is, Li · B (CN) 4 has problems of insufficient electrochemical stability and low electrical conductivity at low temperatures. On the other hand, when X is 4, that is, LiBF 4 has a problem of low electrical conductivity. A compound substituted with another group instead of the fluorine atom (F) has problems of low electrochemical stability and low electrical conductivity. On the other hand, the lithium salt (I) has an effect of sufficient electrochemical stability and high electrical conductivity particularly at a low temperature because the boron atom is substituted with both a fluorine atom and a cyano group.
　リチウム塩（Ｉ）の熱分解温度は１６０℃以上であり３種とも好適に用いることができるが、その中でも、Ｌｉ・ＢＦ2（ＣＮ）2およびＬｉ・ＢＦ（ＣＮ）3は、分解温度が１８０℃以上であるため、より好適である。具体的には、Ｌｉ・ＢＦ2（ＣＮ）2の熱分解温度は１９０℃であり、Ｌｉ・ＢＦ（ＣＮ）3の熱分解温度は２４０℃であった（この熱分解温度は下記実施例に記載の方法で測定した値である。）。特に、Ｌｉ・ＢＦ2（ＣＮ）2は、高い分解温度を有し、それに加え、有機溶媒に溶解させたときの伝導度が他のシアノフルオロボレート塩を同一濃度で溶解させたときの伝導度より高く、また、耐酸化性も十分あるため、特に好適である。 The thermal decomposition temperature of the lithium salt (I) is 160 ° C. or higher, and all three can be suitably used. Among them, Li · BF 2 (CN) 2 and Li · BF (CN) 3 have decomposition temperatures. Since it is 180 degreeC or more, it is more suitable. Specifically, the thermal decomposition temperature of Li · BF 2 (CN) 2 was 190 ° C., and the thermal decomposition temperature of Li · BF (CN) 3 was 240 ° C. (this thermal decomposition temperature is shown in the examples below). It is a value measured by the method described.) In particular, Li · BF 2 (CN) 2 has a high decomposition temperature, and in addition, the conductivity when dissolved in an organic solvent is the conductivity when other cyanofluoroborate salts are dissolved at the same concentration. It is particularly suitable because it is higher and has sufficient oxidation resistance.
　また、Ｌｉ・ＢＦ2（ＣＮ）2およびＬｉ・ＢＦ（ＣＮ）3は、水に対しても安定である。 Li · BF 2 (CN) 2 and Li · BF (CN) 3 are also stable against water.
　本発明の非水電解液に用いられるリチウム塩は上述のリチウム塩（Ｉ）にその他のリチウム塩を混合してもよく、その他のリチウム塩としては、前記リチウム塩（Ｉ）以外の既存のリチウム塩を特に制限無く用いることができる。 The lithium salt used in the non-aqueous electrolyte of the present invention may be mixed with the above-mentioned lithium salt (I) and other lithium salts. As the other lithium salt, existing lithium other than the lithium salt (I) may be used. A salt can be used without particular limitation.
　その他のリチウム塩としては、ＣＦ3ＳＯ3Ｌｉ、ＬｉＮ（ＦＳＯ2）2、ＬｉＮ（ＦＳＯ2）（ＣＦ3ＳＯ2）、ＬｉＮ（ＣＦ3ＳＯ2）2、ＬｉＮ（Ｃ2Ｆ5ＳＯ2）2、リチウム環状１，２－パーフルオロエタンジスルホニルイミド、リチウム環状１，３－パーフルオロプロパンジスルホニルイミド、ＬｉＣ（ＦＳＯ2）3、ＬｉＣ（ＣＦ3ＳＯ2）3、ＬｉＣ（Ｃ2Ｆ5ＳＯ2）3、リチウムビスオキサラトボレート、リチウムジフルオロオキサラトボレート、リチウムテトラフルオロオキサラトホスフェート、リチウムジフルオロビスオキサラトフォスフェート、ＬｉＢＦ3ＣＦ3、ＬｉＢＦ3Ｃ2Ｆ5、ＬｉＰＦ3（ＣＦ3）3、ＬｉＰＦ3（Ｃ2Ｆ5）3等の有機リチウム塩およびＬｉＰＦ6、ＬｉＢＦ4、ＬｉＣｌＯ4などの無機リチウム塩などが挙げられる。 Other lithium salts include CF 3 SO 3 Li, LiN (FSO 2 ) 2 , LiN (FSO 2 ) (CF 3 SO 2 ), LiN (CF 3 SO 2 ) 2 , LiN (C 2 F 5 SO 2 ). 2 , lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropane disulfonylimide, LiC (FSO 2 ) 3 , LiC (CF 3 SO 2 ) 3 , LiC (C 2 F 5 SO 2 ) 3 , lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium tetrafluorooxalate phosphate, lithium difluorobisoxalatophosphate, LiBF 3 CF 3 , LiBF 3 C 2 F 5 , LiPF 3 (CF 3 ) 3 , organic lithium salts such as LiPF 3 (C 2 F 5 ) 3, and LiPF 6 , LiBF 4 , LiClO 4, etc. Examples include inorganic lithium salts.
　前記その他のリチウム塩は１種単独で用いても、あるいは、２種以上を併用してもよい。 The other lithium salts may be used alone or in combination of two or more.
　これらその他のリチウム塩の配合割合は、全リチウム塩中、５０モル％未満であることが好ましく、３０モル％以下であることがより好ましい。ここで、全リチウム塩とは、非水電解液に含まれるリチウム塩の合計のことであり、つまり、前記リチウム塩（Ｉ）とその他のリチウム塩との合計を表わす。 The blending ratio of these other lithium salts is preferably less than 50 mol%, more preferably 30 mol% or less in the total lithium salt. Here, the total lithium salt is the total of lithium salts contained in the non-aqueous electrolyte, that is, the total of the lithium salt (I) and other lithium salts.
　前記その他のリチウム塩を配合した場合、配合する塩によっては非水電解液の粘度が上昇し電気伝導度が低下したり、非水電解液の電気化学安定性および高温安定性が低下したりするおそれがある。そのため、その他のリチウム塩が含まれない態様が好ましい。 When the other lithium salt is blended, depending on the salt to be blended, the viscosity of the non-aqueous electrolyte increases and the electrical conductivity decreases, or the electrochemical stability and high-temperature stability of the non-aqueous electrolyte decrease. There is a fear. Therefore, an embodiment in which no other lithium salt is contained is preferable.
　本発明の非水電解液において、非水電解液に含有される全リチウム塩の含有量は、非水電解液中に０．３～４ｍｏｌ／Ｌであることが好ましく、通常０．３ｍｏｌ／Ｌ以上、より好ましくは０．５ｍｏｌ／Ｌ以上、さらに好ましくは０．７ｍｏｌ／Ｌ以上であり、通常４ｍｏｌ／Ｌ以下、より好ましくは３ｍｏｌ／Ｌ以下、さらに好ましくは１．５ｍｏｌ／Ｌ以下である。この濃度であれば、電流の媒体であるリチウムイオンの濃度が少なすぎず、電解液の粘度の範囲が適切であり、適切な電気伝導度を得ることができる。 In the nonaqueous electrolytic solution of the present invention, the content of all lithium salts contained in the nonaqueous electrolytic solution is preferably 0.3 to 4 mol / L, and usually 0.3 mol / L in the nonaqueous electrolytic solution. As mentioned above, More preferably, it is 0.5 mol / L or more, More preferably, it is 0.7 mol / L or more, Usually, 4 mol / L or less, More preferably, it is 3 mol / L or less, More preferably, it is 1.5 mol / L or less. If it is this density | concentration, the density | concentration of the viscosity of electrolyte solution is appropriate, and the density | concentration of the lithium ion which is a medium of an electric current is too small, and can obtain appropriate electrical conductivity.
　さらに、非水電解液中の前記リチウム塩（Ｉ）の含有量は、好ましくは０．３～４ｍｏｌ／Ｌ、より好ましくは０．５～３ｍｏｌ／Ｌ、さらに好ましくは０．７～１．５ｍｏｌ／Ｌである。 Further, the content of the lithium salt (I) in the non-aqueous electrolyte is preferably 0.3 to 4 mol / L, more preferably 0.5 to 3 mol / L, and still more preferably 0.7 to 1.5 mol. / L.
　《リチウム塩（Ｉ）の製造方法》
　前記リチウム塩（Ｉ）は、公知の方法で合成することが可能であり、例えば、アセトニトリルおよびアセトンなどの有機溶媒にリチウム金属のシアン化合物を溶解させＢＦ3ガスを吹き込む方法、または、リチウム金属のシアン化合物を、アセトニトリル、ジエチルエーテル、テトラヒドロフランおよびジメトキシエタン等の非プロトン性溶媒の存在下で、三フッ化ホウ素エーテルＢＦ3・ＯＥｔ2等のＢＦ3付加化合物と反応させる方法で合成することができる。 << Production Method of Lithium Salt (I) >>
The lithium salt (I) can be synthesized by a known method. For example, a lithium metal cyanide compound is dissolved in an organic solvent such as acetonitrile and acetone, and BF 3 gas is blown, or a lithium metal It can be synthesized by a method in which a cyanide compound is reacted with a BF 3 addition compound such as boron trifluoride ether BF 3 · OEt 2 in the presence of an aprotic solvent such as acetonitrile, diethyl ether, tetrahydrofuran and dimethoxyethane. .
　また、上記方法の他には、カリウム、ナトリウム、マグネシウムおよびカルシウム等の、リチウム以外のアルカリ金属またはアルカリ土類金属のシアン化合物を、有機溶媒に溶解させ得られた溶液に上述のＢＦ3ガスを吹き込み、または、非プロトン性溶媒の存在下で三フッ化ホウ素エーテルＢＦ3・ＯＥｔ2等のＢＦ3付加化合物を作用させ、シアノフルオロボレートの対応するアルカリ金属またはアルカリ土類金属塩を合成し、これに、水酸化リチウム、炭酸リチウム、ハロゲン化リチウムなどの無機リチウム塩を作用させることで塩交換を行い、前記リチウム塩（Ｉ）を合成する方法などがある。 In addition to the above method, potassium, sodium, such as magnesium and calcium, cyanide of an alkali metal or alkaline earth metal other than lithium, the above BF 3 gas in the resulting solution is dissolved in an organic solvent BF 3 adduct such as boron trifluoride ether BF 3 · OEt 2 is allowed to act in the presence of an aprotic solvent to synthesize a corresponding alkali metal or alkaline earth metal salt of cyanofluoroborate, This includes a method of synthesizing the lithium salt (I) by performing salt exchange by allowing an inorganic lithium salt such as lithium hydroxide, lithium carbonate, or lithium halide to act.
　また、合成されたリチウム塩（Ｉ）を本発明の非水電解液に用いる際には、例えば、水洗、乾燥などを十分に行い、不純物を十分除去することが好ましい。具体的には、水分濃度は１０００ｐｐｍ以下、Ｌｉ以外の金属濃度はＮａが２０ｐｐｍ以下、Ｋが１０ｐｐｍ以下、Ｃａが１０ｐｐｍ以下、Ｆｅが３ｐｐｍ以下、Ｐｂが１０ｐｐｍ以下となるよう精製して用いることが好ましい（いずれもリチウム塩（Ｉ）を１００質量％とする）。 Further, when the synthesized lithium salt (I) is used for the non-aqueous electrolyte of the present invention, it is preferable to sufficiently remove impurities by, for example, sufficiently washing with water and drying. Specifically, the metal concentration other than Li is 1000 ppm or less, Na is 20 ppm or less, K is 10 ppm or less, Ca is 10 ppm or less, Fe is 3 ppm or less, and Pb is 10 ppm or less. Preferable (both lithium salt (I) is 100% by mass).
　＜非水溶媒＞
　電池用電解液には、１）使用範囲の電気化学安定性と、２）電解質塩への高い溶解性と、３）低粘性などによる高い電気伝導性が要求される。特にリチウムイオン電池は充放電の電位が０～４．５Ｖ　ｖｓ　Ｌｉ+／Ｌｉ程度と他の電池に比して非常に広く、用いることができる溶媒は限定される。 <Nonaqueous solvent>
Battery electrolytes are required to have 1) electrochemical stability in the range of use, 2) high solubility in electrolyte salts, and 3) high electrical conductivity due to low viscosity. In particular, lithium ion batteries have a charge / discharge potential of about 0 to 4.5 V vs. Li + / Li, which is very wide compared to other batteries, and the solvents that can be used are limited.
　本発明の非水電解液に用いられる有機溶媒（非水溶媒）は、鎖状カーボネート、環状カーボネート、鎖状エステル、ラクトンおよびエーテルよりなる群から選ばれる少なくとも１種を含む。なお、この非水溶媒は水を含まないものである。本発明において使用可能な有機溶媒としては以下の有機溶媒（非水溶媒)が例示される。 The organic solvent (nonaqueous solvent) used in the nonaqueous electrolytic solution of the present invention contains at least one selected from the group consisting of a chain carbonate, a cyclic carbonate, a chain ester, a lactone and an ether. This non-aqueous solvent does not contain water. Examples of the organic solvent that can be used in the present invention include the following organic solvents (non-aqueous solvents).
　鎖状カーボネートとしては、炭素数３～６の鎖状カーボネートが好ましい。具体的な鎖状カーボネートとしては、炭酸ジメチル、炭酸エチルメチル、炭酸ジエチルが挙げられる。 As the chain carbonate, a chain carbonate having 3 to 6 carbon atoms is preferable. Specific examples of the chain carbonate include dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.
　環状カーボネートとしては、炭素数３～６の環状カーボネートが好ましい。具体的な環状カーボネートとしては、炭酸エチレン、炭酸プロピレンが挙げられる。 As the cyclic carbonate, a cyclic carbonate having 3 to 6 carbon atoms is preferable. Specific examples of the cyclic carbonate include ethylene carbonate and propylene carbonate.
　鎖状エステルとしては、炭素数３～６の鎖状エステルが好ましい。具体的な鎖状エステルとしては、プロピオン酸エチル、プロピオン酸メチル、酢酸エチル、酢酸メチルが挙げられる。 The chain ester is preferably a chain ester having 3 to 6 carbon atoms. Specific examples of the chain ester include ethyl propionate, methyl propionate, ethyl acetate, and methyl acetate.
　ラクトンとしては、炭素数３～６のラクトンが挙げられる。具体的なラクトンとしては、γ－ブチロラクトンが挙げられる。 Examples of the lactone include lactones having 3 to 6 carbon atoms. Specific examples of the lactone include γ-butyrolactone.
　エーテルとしては、炭素数３～８のエーテルが好ましい。具体的なエーテルとしては、ジメトキシエタン、エトキシメトキシエタン、ジエトキシエタンおよびトリエチレングリコールジメチルエーテルが挙げられる。 The ether is preferably an ether having 3 to 8 carbon atoms. Specific ethers include dimethoxyethane, ethoxymethoxyethane, diethoxyethane, and triethylene glycol dimethyl ether.
　以上の例示の有機溶媒（非水溶媒)において、電解液の調製時、または電解液の使用時に固体であるものについては、液状である上記他の有機溶媒（非水溶媒）と混合して液状の混合溶媒として使用することができる。 Of the organic solvents (nonaqueous solvents) exemplified above, those that are solid when the electrolytic solution is prepared or used are mixed with the above-mentioned other organic solvents (nonaqueous solvents) that are liquid. It can be used as a mixed solvent.
　上記以外の有機溶媒は通常、電気化学安定性が不十分であったり、電解質塩の溶解度が小さい、粘度が高く電気伝導度が小さいなどの理由で電解液として適さない。 Organic solvents other than the above are usually unsuitable as electrolytes because of insufficient electrochemical stability, low solubility of electrolyte salts, high viscosity and low electrical conductivity.
　上記溶媒は１種単独で用いても、あるいは、２種以上を併用してもよい。例えば、環状カーボネート類のような高誘電率の溶媒と鎖状カーボネートおよび鎖状エステル類のような低粘度の溶媒とを組み合わせることで、良好な溶解性と高い電気伝導性が得られることが知られていて、これらを好適に用いることができる。 The above solvents may be used alone or in combination of two or more. For example, it is known that good solubility and high electrical conductivity can be obtained by combining a high dielectric constant solvent such as cyclic carbonates with a low viscosity solvent such as chain carbonates and chain esters. These can be suitably used.
　その中でも、リチウム塩（Ｉ）の溶解性と得られる電解液の性能（優れた電気伝導度および電気化学安定性等）とを考慮すると、非水溶媒として鎖状カーボネートまたは環状カーボネートを使用することが好ましく、特に、鎖状カーボネートと環状カーボネートとの混合溶媒を使用することが好ましい。 Among them, in consideration of the solubility of the lithium salt (I) and the performance of the obtained electrolyte (excellent electrical conductivity and electrochemical stability), a chain carbonate or a cyclic carbonate should be used as a non-aqueous solvent. In particular, it is preferable to use a mixed solvent of a chain carbonate and a cyclic carbonate.
　前記混合溶媒を使用する場合、混合溶媒中の鎖状カーボネート含有割合が体積％（２３℃）として１５％以上であると電解液の粘度を調整し易く、かつ電気伝導度を高くすることができるために好適である。また、鎖状カーボネート含有割合が体積％（２３℃）として９０％以下であると、溶媒の誘電率の低下による電気伝導度の低下を少なくすることができる。そのため、混合溶媒とする場合には、鎖状カーボネート含有割合が１５％以上９０％以下、環状カーボネート含有割合が１０％以上８５％以下であることが好ましく、鎖状カーボネート含有割合が２０％以上８５％以下、環状カーボネート含有割合が１５％以上８０％以下であることがより好ましく、鎖状カーボネート含有割合が２５％以上８０％以下、環状カーボネート含有割合が２０％以上７５％以下であることがさらに好ましい（ただし、２３℃における鎖状カーボネートと環状カーボネートとの合計体積％は１００％とする。）。上記の混合溶媒の中でも、環状カーボネートとして炭酸エチレンを使用した場合には、体積％（２３℃）として、鎖状カーボネート含有割合が４０％以上８５％以下、炭酸エチレン含有割合が１５％以上６０％以下であることが好ましく、鎖状カーボネート含有割合が４５％以上８０％以下、炭酸エチレン含有割合が２０％以上５５％以下であることがより好ましい。 When the mixed solvent is used, the viscosity of the electrolytic solution can be easily adjusted and the electrical conductivity can be increased when the linear carbonate content in the mixed solvent is 15% or more by volume% (23 ° C.). Therefore, it is suitable. In addition, when the chain carbonate content is 90% or less in terms of volume% (23 ° C.), a decrease in electrical conductivity due to a decrease in the dielectric constant of the solvent can be reduced. For this reason, when a mixed solvent is used, the chain carbonate content is preferably 15% to 90%, the cyclic carbonate content is preferably 10% to 85%, and the chain carbonate content is 20% to 85%. %, More preferably the cyclic carbonate content is 15% to 80%, the chain carbonate content is 25% to 80%, and the cyclic carbonate content is 20% to 75%. Preferred (however, the total volume% of the chain carbonate and cyclic carbonate at 23 ° C. is 100%). Among the above mixed solvents, when ethylene carbonate is used as the cyclic carbonate, as a volume% (23 ° C.), the chain carbonate content is 40% or more and 85% or less, and the ethylene carbonate content is 15% or more and 60%. The chain carbonate content is preferably 45% or more and 80% or less, and the ethylene carbonate content is more preferably 20% or more and 55% or less.
　また、高い電気伝導度を得ることができ、かつ蒸気圧が低いことから、非水溶媒としてラクトンを使用することも好ましい。 It is also preferable to use a lactone as the non-aqueous solvent because high electrical conductivity can be obtained and the vapor pressure is low.
　この非水溶媒を含む非水電解液を電池に適用することで、高温での安定性と低温での高伝導率とを両立した電池を提供することができる。 By applying a non-aqueous electrolyte solution containing this non-aqueous solvent to the battery, it is possible to provide a battery that achieves both stability at high temperatures and high conductivity at low temperatures.
　＜添加物＞
　本発明の非水電解液はまた、既存の電池用または電気二重層キャパシタの電解液に用いられる添加物を含んでいても良い。リチウムイオン電池用電解液は、難燃化およびサイクル特性向上等の目的で様々な添加剤を含んでいるが、当該非水電解液は既存の添加剤がそのまま使える。添加剤の例としては二重結合を含む不飽和カーボネート、フッ化カーボネートなどが挙げられる。 <Additives>
The non-aqueous electrolyte of the present invention may also contain an additive used for an existing battery or an electric double layer capacitor electrolyte. The electrolyte for a lithium ion battery contains various additives for the purpose of flame retardancy and cycle characteristics improvement, but the existing additive can be used as it is for the non-aqueous electrolyte. Examples of the additive include unsaturated carbonates containing double bonds and fluorinated carbonates.
　二重結合を含む不飽和カーボネートの具体的な例としては、炭酸ビニレン、炭酸ビニルエチレン等が挙げられ、フッ化カーボネートの具体的な例としては、フッ素化ジメチルカーボネート誘導体、フッ素化エチルメチルカーボネート誘導体、フッ素化ジエチルカーボネート誘導体等が挙げられる。 Specific examples of the unsaturated carbonate containing a double bond include vinylene carbonate and vinyl ethylene carbonate. Specific examples of the fluorinated carbonate include a fluorinated dimethyl carbonate derivative and a fluorinated ethyl methyl carbonate derivative. And fluorinated diethyl carbonate derivatives.
　≪非水電解液の特性≫
　本発明の非水電解液が、高温下でのサイクル特性を大幅に改善できる理由は必ずしも明確ではないが、以下のように考えられる。 ≪Nonaqueous electrolyte characteristics≫
The reason why the nonaqueous electrolytic solution of the present invention can greatly improve the cycle characteristics at high temperatures is not necessarily clear, but is considered as follows.
　現在主流である六フッ化フォスフェート・リチウム塩（ＬｉＰＦ6）は６０℃付近から分解を始めると共に、本質的には水に対して不安定であり、水分と反応して分解するなど鋭敏な化合物である。リチウムイオン電池などは充電時に電極で溶媒などが反応し、その反応で水分が容易に生じうる。そのため添加剤などによって反応を抑えても、本質的には電解質塩の劣化は進行すると考えられる。それに対し本発明で用いるリチウム塩（Ｉ）の熱分解温度は１６０℃以上であり、好適な化合物の熱分解温度は１８０℃以上であり、より好適な化合物の熱分解温度は２００℃以上である（この熱分解温度は下記実施例に記載の方法で測定した値である。）。したがって、化合物の本質的な安定性が異なるために、高温下で安定であると考えられる。 At present, the mainstream hexafluorophosphate lithium salt (LiPF 6 ) starts to decompose at around 60 ° C. and is essentially unstable to water, and is a sensitive compound that decomposes by reacting with moisture. It is. A lithium ion battery or the like reacts with a solvent or the like at the time of charging, and moisture can easily be generated by the reaction. Therefore, even if the reaction is suppressed by an additive or the like, the deterioration of the electrolyte salt is considered to proceed essentially. On the other hand, the thermal decomposition temperature of the lithium salt (I) used in the present invention is 160 ° C or higher, the thermal decomposition temperature of a suitable compound is 180 ° C or higher, and the thermal decomposition temperature of a more preferable compound is 200 ° C or higher. (This thermal decomposition temperature is a value measured by the method described in the Examples below). Therefore, it is considered stable at high temperatures because of the inherent stability of the compounds.
　また、本発明の非水電解液が高い伝導度を示し、特に低温であっても高イオン伝導度を示す理由は必ずしも明確でないが、電解質塩であるリチウム塩（Ｉ）のアニオンのイオン径および分子量が、特に六フッ化フォスフェートアニオンのイオン径および分子量に対して比較的小さいこと、対称性が小さい為、析出しにくいことおよびアニオンの極性が小さく化合物間の相互作用が小さいことが原因であると考えられる。 The reason why the non-aqueous electrolyte of the present invention exhibits high conductivity, particularly high ion conductivity even at low temperatures, is not necessarily clear, but the ion diameter of the anion of the lithium salt (I) that is an electrolyte salt and This is because the molecular weight is relatively small, especially with respect to the ion diameter and molecular weight of the hexafluorophosphate anion, and because the symmetry is small, it is difficult to precipitate and the polarity of the anion is small and the interaction between compounds is small. It is believed that there is.
　〔蓄電デバイス〕
　前記非水電解液は、リチウム電池（リチウム一次電池）、リチウムイオン電池（リチウム二次電池）およびリチウムイオンキャパシタ等の蓄電デバイスに使用することができる。その中でも、リチウム電池およびリチウムイオン電池として用いることが更に好ましく、リチウムイオン電池として用いることが最も好ましい。また、非水電解液は、液体状のものだけでなくゲル化して使用してもよい。更に本発明の非水電解液は固体高分子電解質用としても使用できる。 [Power storage device]
The non-aqueous electrolyte can be used for power storage devices such as lithium batteries (lithium primary batteries), lithium ion batteries (lithium secondary batteries), and lithium ion capacitors. Among these, it is more preferable to use as a lithium battery and a lithium ion battery, and it is most preferable to use as a lithium ion battery. Further, the nonaqueous electrolytic solution may be used in a gel form as well as in a liquid form. Furthermore, the non-aqueous electrolyte of the present invention can be used for a solid polymer electrolyte.
　本発明の蓄電デバイスは、非水電解液にリチウム塩（Ｉ）を用いることで、６０℃以上の高温で保存しても劣化が少なく、常温から低温まで既存の電解液以上の電気伝導度を持ち、電気化学的にも安定な電解液とする事ができる。 The electricity storage device of the present invention uses lithium salt (I) as a non-aqueous electrolyte, so that it has little deterioration even when stored at a high temperature of 60 ° C. or higher, and has an electrical conductivity higher than that of an existing electrolyte from room temperature to low temperature. It can be made into an electrolyte that is electrochemically stable.
　＜リチウム電池＞
　リチウム電池は、負極と、正極と、正極と負極との間に配されたセパレータと、前記の本発明の非水電解液とを備えるものである。 <Lithium battery>
The lithium battery includes a negative electrode, a positive electrode, a separator disposed between the positive electrode and the negative electrode, and the nonaqueous electrolytic solution of the present invention.
　リチウム電池は、非水電解液以外の構成については公知のリチウム電池と同様であり、通常は、前記非水電解液が含浸されている多孔膜を介し正極と負極とが積層され、これらがケースに収納された形態を有する。従って、リチウム電池の形状は特に制限されるものではなく、円筒型、角形、ラミネート型、コイン型、大型等の何れであってもよい。 The lithium battery has the same configuration as the known lithium battery except for the non-aqueous electrolyte. Usually, the positive electrode and the negative electrode are laminated through a porous film impregnated with the non-aqueous electrolyte, and these are the cases. It has the form stored in. Therefore, the shape of the lithium battery is not particularly limited, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.
　負極には、活物質として、リチウムおよびリチウム合金からなる群より選ばれる少なくとも１種が用いられる。 In the negative electrode, at least one selected from the group consisting of lithium and lithium alloys is used as an active material.
　正極は、正極活物質を含有し、好ましくは、さらに導電材および結着剤を含む。正極活物質としては、リチウム電池の分野で常用される材料をそのまま使用でき、その中でも、二酸化マンガンなどの金属酸化物、フッ化黒鉛、塩化チオニルなどが好適に使用できる。二酸化マンガンは、放電特性が良好であり、特に好ましい。 The positive electrode contains a positive electrode active material, and preferably further contains a conductive material and a binder. As the positive electrode active material, materials commonly used in the field of lithium batteries can be used as they are, and among them, metal oxides such as manganese dioxide, graphite fluoride, thionyl chloride and the like can be preferably used. Manganese dioxide is particularly preferable because of its good discharge characteristics.
　リチウム塩（Ｉ）を用いた本発明の非水電解液は、６０℃以上の高温で保存しても劣化が少なく、常温から低温まで既存のリチウム電池以上の電流で放電可能な電池とする事ができる。
＜リチウムイオン電池＞
　リチウムイオン電池は、リチウムイオンを吸蔵および放出し得る、負極および正極と、正極と負極との間に配されたセパレータと、前記の本発明の非水電解液とを備えるものである。 The non-aqueous electrolyte of the present invention using a lithium salt (I) is a battery that can be discharged at a current higher than that of an existing lithium battery from room temperature to low temperature with little deterioration even when stored at a high temperature of 60 ° C. or higher. Can do.
<Lithium ion battery>
The lithium ion battery includes a negative electrode and a positive electrode that can occlude and release lithium ions, a separator disposed between the positive electrode and the negative electrode, and the nonaqueous electrolytic solution of the present invention.
　リチウムイオン電池は、非水電解液以外の構成については、公知のリチウムイオン電池と同様であり、通常は、前記非水電解液が含浸されている多孔膜を介し正極と負極とが積層され、これらがケースに収納された形態を有する。従って、リチウムイオン電池の形状は特に制限されるものではなく、円筒型、角形、ラミネート型、コイン型、大型等の何れであってもよい。 The lithium ion battery is the same as the known lithium ion battery in terms of the configuration other than the non-aqueous electrolyte, and usually the positive electrode and the negative electrode are laminated through the porous film impregnated with the non-aqueous electrolyte, These have the form accommodated in the case. Therefore, the shape of the lithium ion battery is not particularly limited, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.
　リチウムイオン電池に使用する負極は、集電体上に負極活物質層を有する。負極活物質としては、電気化学的にリチウムイオンを吸蔵および放出可能なものであれば、特に制限はない。その具体例としては、炭素質材料、合金系材料、リチウム含有金属複合酸化物材料等が挙げられる。これらは１種を単独で用いてもよく、また２種以上を任意に組み合わせて併用してもよい。 A negative electrode used for a lithium ion battery has a negative electrode active material layer on a current collector. The negative electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. Specific examples thereof include carbonaceous materials, alloy-based materials, lithium-containing metal composite oxide materials, and the like. These may be used individually by 1 type, and may be used together combining 2 or more types arbitrarily.
　正極活物質としては、電気化学的にリチウムイオンを吸蔵および放出可能なものであれば特に制限されず用いることができる。正極活物質としてはリチウムと少なくとも１種の遷移金属とを含有する物質が好ましい。具体例としては、リチウム遷移金属複合酸化物、リチウム含有遷移金属リン酸化合物が挙げられる。これらの正極活物質は、１種を単独で用いてもよく、また、２種以上を任意に組み合わせて併用してもよい。 Any positive electrode active material that can electrochemically occlude and release lithium ions can be used without any particular limitation. The positive electrode active material is preferably a material containing lithium and at least one transition metal. Specific examples include lithium transition metal composite oxides and lithium-containing transition metal phosphate compounds. These positive electrode active materials may be used alone or in any combination of two or more.
　リチウムイオン電池は、充電終止電圧が４．２Ｖ以上、特に４．３Ｖ以上の場合にも高温での電気化学特性に優れている。また、本発明におけるリチウムイオン電池は、－４０～１００℃で充放電することができる。 Lithium ion batteries have excellent electrochemical characteristics at high temperatures even when the end-of-charge voltage is 4.2 V or higher, particularly 4.3 V or higher. In addition, the lithium ion battery according to the present invention can be charged and discharged at −40 to 100 ° C.
　リチウム塩（Ｉ）を用いた本発明の非水電解液は、６０℃以上の高温で保存しても劣化が少なく、常温から低温まで既存のリチウムイオン電池以上の電流で充放電可能な二次電池とする事ができる。 The non-aqueous electrolyte of the present invention using a lithium salt (I) is a secondary that can be charged and discharged at a current higher than that of an existing lithium ion battery from room temperature to low temperature even when stored at a high temperature of 60 ° C. or higher. It can be a battery.
　＜リチウムイオンキャパシタ＞
　リチウムイオンキャパシタ（ＬＩＣ）とは、負極にグラファイト等の炭素材料を用い、それへのリチウムイオンのインターカレーションを利用してエネルギーを貯蔵する蓄電デバイスである。正極は、例えば活性炭電極と電解液との間の電気二重層を利用したもの、π共役高分子電極のドープ／脱ドープ反応を利用したもの等が挙げられる。 <Lithium ion capacitor>
A lithium ion capacitor (LIC) is a power storage device that uses a carbon material such as graphite as a negative electrode and stores energy using lithium ion intercalation thereto. Examples of the positive electrode include those using an electric double layer between an activated carbon electrode and an electrolytic solution, those using a π-conjugated polymer electrode doping / dedoping reaction, and the like.
　電解液として前述の電解液が使用されるため、ＬＩＣは、高温での電気化学安定性と低温での高伝導率の両立することができる。 Since the above-described electrolytic solution is used as the electrolytic solution, LIC can achieve both electrochemical stability at high temperature and high conductivity at low temperature.
　以下、実施例を挙げて本発明を更に詳細に説明するが、本発明はこれらに限定されるものではない。 Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.
　（１）電気伝導度
　試料溶液１０ｍｌをフッ素樹脂（ＰＦＡ）製の小型ビーカーに取り、ＴＤＫ社製電気伝導度測定メーターにより測定した。伝導度のキャリブレーションはキシダ化学株式会社より購入した１ｍｏｌ／Ｌ　ＬｉＰＦ6の炭酸エチレン－炭酸ジエチルの混合溶液（１：１）の伝導度０．７Ｓ／ｍおよび１ｍｏｌ／Ｌ　ＬｉＢＦ4の炭酸エチレン－炭酸ジエチルの混合溶液（１：１）の伝導度０．３９Ｓ／ｍにより校正した。 (1) Electric conductivity 10 ml of the sample solution was placed in a small beaker made of fluororesin (PFA) and measured with an electric conductivity measuring meter manufactured by TDK. Conductivity calibration was conducted using a 1 mol / L LiPF 6 ethylene carbonate-diethyl carbonate mixed solution (1: 1) conductivity 0.7 S / m and 1 mol / L LiBF 4 ethylene carbonate purchased from Kishida Chemical Co., Ltd. Calibration was performed with a conductivity of 0.39 S / m of a mixed solution of diethyl carbonate (1: 1).
　（２）電気化学測定
　試料溶液適量（～２ｍｌ）をＢＡＳ社製ＶＣ－４ボルタンメトリー用セルにいれ、グラッシーカーボン電極、白金電極およびＡｇ／Ａｇ+型参照電極を用いＡｕｔｏｌａｂ社製ポテンシオスタットでサイクリックボルタンメトリ測定を行い、電気化学安定性を評価した。 (2) Electrochemical measurement An appropriate amount (up to 2 ml) of the sample solution was put into a cell for VC-4 voltammetry manufactured by BAS, and squeezed with a potentiostat manufactured by Autolab using a glassy carbon electrode, a platinum electrode and an Ag / Ag + type reference electrode. Click voltammetry was performed to evaluate electrochemical stability.
　（３）充電容量および放電容量
　初期充放電特性の評価で測定した充電容量および放電容量、ならびに、低温動作性の評価で測定した放電容量は、充放電試験装置（北斗電工製HJ0501SD8）で測定した。充放電試験の条件は、
充電；０．２Ｃ、４．２Ｖ定電流定電圧（０．０５Ｃ電流減衰）
放電；０．２Ｃ、２．７Ｖ定電流
で行った。そして、この条件で繰り返し充放電を行い、３回目の結果を初期充放電特性とした。 (3) Charge capacity and discharge capacity The charge capacity and discharge capacity measured in the initial charge / discharge characteristics evaluation and the discharge capacity measured in the low temperature operability evaluation were measured with a charge / discharge test device (HJ0501SD8 manufactured by Hokuto Denko). . The conditions for the charge / discharge test are:
Charge: 0.2C, 4.2V constant current constant voltage (0.05C current decay)
Discharge: performed at 0.2 C, 2.7 V constant current. And charging / discharging was repeated on these conditions, and the 3rd result was made into the initial stage charging / discharging characteristic.
　（４）抵抗
　高温保存性能の評価および低温動作性の評価で測定した抵抗は、東陽テクニカ製VersaSTAT4で測定した。 (4) Resistance The resistance measured in the evaluation of the high temperature storage performance and the evaluation of the low temperature operability was measured with VersaSTAT4 manufactured by Toyo Technica.
　〔１．リチウム塩の熱分解温度〕
　Ｌｉ・ＢＦ2（ＣＮ）2、Ｌｉ・ＢＦ（ＣＮ）3、ＬｉＰＦ6およびＬｉＢＦ4約１ｇを、それぞれフッ素樹脂（ＰＦＡ）製の容器に入れ、Fisher Scientific社製真空乾燥器で真空下加熱し、容器中の試料が変色する等変化が認められた温度を測定した。結果を表１に示す。 [1. Thermal decomposition temperature of lithium salt)
About 1 g of Li · BF 2 (CN) 2 , Li · BF (CN) 3 , LiPF 6 and LiBF 4 are put in a fluororesin (PFA) container, respectively, and heated under vacuum in a Fisher Scientific vacuum dryer. The temperature at which a change such as a discoloration of the sample in the container was observed was measured. The results are shown in Table 1.
　〔２．非水電解液の温度の違いによる電気伝導度の比較〕
　［実施例１－１］
　炭酸エチレン３３ｇに炭酸ジエチル２５ｍｌを加え溶解させ、さらに、Ｌｉ・ＢＦ2（ＣＮ）2５．３９ｇを加え攪拌し、完全に溶解させ、炭酸エチレンと炭酸ジエチルとの１：１（２３℃体積比）混合溶媒にＬｉ・ＢＦ2（ＣＮ）2が１ｍｏｌ／Ｌの濃度で溶解した非水電解液を作製した。 [2. Comparison of electrical conductivity due to temperature difference of non-aqueous electrolyte)
[Example 1-1]
25 ml of diethyl carbonate was added to 33 g of ethylene carbonate and dissolved, and 5.39 g of Li · BF 2 (CN) 2 was added and stirred to dissolve completely. 1: 1 (23 ° C. volume ratio) of ethylene carbonate and diethyl carbonate ) A non-aqueous electrolyte solution in which Li · BF 2 (CN) 2 was dissolved in a mixed solvent at a concentration of 1 mol / L was prepared.
　得られた非水電解液の２３℃、０℃および－１０℃での電気伝導度、ならびに、電気化学安定性を測定した。測定結果を表１に示す。前記非水電解液のサイクリックボルタモグラムの測定結果を図１に示す。 The electrical conductivity and electrochemical stability at 23 ° C., 0 ° C. and −10 ° C. of the obtained nonaqueous electrolytic solution were measured. The measurement results are shown in Table 1. The measurement result of the cyclic voltammogram of the non-aqueous electrolyte is shown in FIG.
　［実施例１－２］
　Ｌｉ・ＢＦ（ＣＮ）3５．７４ｇを用いたこと以外は実施例１－１と同様にして、炭酸エチレンと炭酸ジエチルとの１：１（２３℃体積比）混合溶媒にＬｉ・ＢＦ（ＣＮ）3が１ｍｏｌ／Ｌの濃度で溶解した非水電解液を作製した。 [Example 1-2]
Except for using 5.74 g of Li · BF (CN) 3, the mixture was mixed with a mixed solvent of ethylene carbonate and diethyl carbonate in a 1: 1 (23 ° C. volume ratio) mixed solvent of Li · BF (CN). ) A nonaqueous electrolytic solution in which 3 was dissolved at a concentration of 1 mol / L was prepared.
　　得られた非水電解液の２３℃、０℃および－１０℃での電気伝導度、ならびに、電気化学安定性を測定した。測定結果を表１に示す。前記非水電解液のサイクリックボルタモグラムの測定結果を図２に示す。 The electrical conductivity and electrochemical stability at 23 ° C., 0 ° C. and −10 ° C. of the obtained non-aqueous electrolyte were measured. The measurement results are shown in Table 1. The measurement result of the cyclic voltammogram of the non-aqueous electrolyte is shown in FIG.
　［比較例１－１］
　キシダ化学株式会社より購入した１ｍｏｌ／Ｌ　ＬｉＰＦ6の炭酸エチレン－炭酸ジエチルの混合溶液（１：１）の２３℃、０℃および－１０℃での電気伝導度、ならびに、電気化学安定性を測定した。測定結果を表１に示す。 [Comparative Example 1-1]
Measures electrical conductivity and electrochemical stability of a 1 mol / L LiPF 6 ethylene carbonate-diethyl carbonate mixed solution (1: 1) purchased from Kishida Chemical Co., Ltd. at 23 ° C, 0 ° C and -10 ° C. did. The measurement results are shown in Table 1.
　［比較例１－２］
　キシダ化学株式会社より購入した炭酸エチレンと炭酸ジエチルとの１：１混合溶媒にＬｉＢＦ4が１ｍｏｌ／Ｌの濃度で溶解した非水電解液の２３℃、０℃および－１０℃での電気伝導度、ならびに、電気化学安定性を測定した。測定結果を表１に示す。 [Comparative Example 1-2]
Electrical conductivity at 23 ° C, 0 ° C and -10 ° C of non-aqueous electrolyte in which LiBF 4 was dissolved at a concentration of 1 mol / L in a 1: 1 mixed solvent of ethylene carbonate and diethyl carbonate purchased from Kishida Chemical Co., Ltd. As well as the electrochemical stability. The measurement results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
 　表１から分かるとおり本発明のシアノフルオロボレート・リチウム塩を用いた非水電解液は、電解質塩としてＬｉＰＦ6またはＬｉＢＦ4を用いた従来の非水電解液と比較して、低温でも電気伝導度の低下が小さく、低温での使用に好適である。
Figure JPOXMLDOC01-appb-T000001
 As can be seen from Table 1, the nonaqueous electrolytic solution using the cyanofluoroborate / lithium salt of the present invention has an electrical conductivity even at a low temperature as compared with the conventional nonaqueous electrolytic solution using LiPF 6 or LiBF 4 as the electrolyte salt. Is suitable for use at low temperatures.
　また、本発明の非水電解液は、従来の非水電解液と室温で同等の電気伝導度および電気化学安定性を持ち、電解質塩の熱分解温度が比較的高いため、作動温度領域が広い、リチウムイオン電池用電解液またはリチウムイオンキャパシタ用電解液等として好適に用いることができる。 In addition, the non-aqueous electrolyte of the present invention has the same electrical conductivity and electrochemical stability at room temperature as the conventional non-aqueous electrolyte, and the electrolyte salt has a relatively high thermal decomposition temperature, so that the operating temperature range is wide. It can be suitably used as a lithium ion battery electrolyte or a lithium ion capacitor electrolyte.
　〔３．非水電解液の溶媒の違いによる電気伝導度の比較〕
　［実施例２－１］
　Ｌｉ・ＢＦ2（ＣＮ）2０．５２ｇをフッ素樹脂系の容器に入れ、γ－ブチロラクトン（以下、ＧＢＬともいう）を加えて溶解し１０ｍｌにし、ＧＢＬ溶媒にＬｉ・ＢＦ2（ＣＮ）2が０．５ｍｏｌ／Ｌの濃度で溶解した非水電解液を作製した。 [3. Comparison of electrical conductivity depending on the solvent of non-aqueous electrolyte)
[Example 2-1]
Add 0.52 g of Li · BF 2 (CN) 2 into a fluororesin container, add γ-butyrolactone (hereinafter also referred to as GBL) to dissolve to 10 ml, and Li · BF 2 (CN) 2 is added to the GBL solvent. A nonaqueous electrolytic solution dissolved at a concentration of 0.5 mol / L was prepared.
　得られた非水電解液の２３℃での電気伝導度を測定した。結果を表２に示す。 The electrical conductivity at 23 ° C. of the obtained non-aqueous electrolyte was measured. The results are shown in Table 2.
　[実施例２－２～２－１５]
　リチウム塩の種類および濃度、ならびに、非水溶媒の種類を表２または３に記載したとおりに変更したこと以外は実施例２－１と同様にして、非水電解液を作製し、２３℃での電気伝導度を測定した。結果を表２または３に示す。なお、Ｌｉ・ＢＦ2（ＣＮ）2は、電解液の濃度を０．５ｍｏｌ／Ｌとする時０．５２ｇ、１．０ｍｏｌ／Ｌとする時１．０４ｇ、２．０ｍｏｌ／Ｌとする時２．０８ｇ使用し、Ｌｉ・ＢＦ（ＣＮ）3は、電解液の濃度を０．５ｍｏｌ／Ｌとする時０．５８ｇ、１．０ｍｏｌ／Ｌとする時１．１５ｇ使用した。

[Examples 2-2 to 2-15]
A non-aqueous electrolyte was prepared in the same manner as in Example 2-1, except that the type and concentration of the lithium salt and the type of the non-aqueous solvent were changed as described in Table 2 or 3. The electrical conductivity of was measured. The results are shown in Table 2 or 3. Li · BF 2 (CN) 2 is 0.52 g when the concentration of the electrolytic solution is 0.5 mol / L, 1.04 g when the concentration is 1.0 mol / L, and 2 when the concentration is 2.0 mol / L. 0.08 g was used, and Li · BF (CN) 3 was used at 0.58 g when the concentration of the electrolytic solution was 0.5 mol / L and 1.15 g when 1.0 mol / L was used.

Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000003
 　上記表２および３に示すようにシアノフルオロボレート・リチウム塩であるＬｉ・ＢＦ2（ＣＮ）2およびＬｉ・ＢＦ（ＣＮ）3は、ラクトン、エーテル、鎖状カーボネートおよび環状カーボネートの有機溶媒に対し広い濃度で溶解し、高い電気伝導度を示す。そのため、リチウムイオン電池用電解液またはリチウムイオンキャパシタ用電解液等として好適に用いることができる。
Figure JPOXMLDOC01-appb-T000003
 As shown in Tables 2 and 3 above, Li · BF 2 (CN) 2 and Li · BF (CN) 3 , which are cyanofluoroborate / lithium salts, are used for organic solvents such as lactones, ethers, chain carbonates and cyclic carbonates. It dissolves in a wide concentration and shows high electrical conductivity. Therefore, it can be suitably used as an electrolyte for lithium ion batteries or an electrolyte for lithium ion capacitors.
　〔４．電池性能評価〕
　[実施例３]
　正極は、活物質としてＬｉＮｉ1/3Ｃｏ1/3Ｍｎ1/3Ｏ2９３部、導電材としてアセチレンブラック４部、および、バインダーとしてポリビニリデンフルオライド３部をスラリー状にし、集電箔にアプリケーターで塗工し、１２０℃で１０分乾燥後プレスして作製した。 [4. Battery performance evaluation)
[Example 3]
In the positive electrode, 93 parts of LiNi 1/3 Co 1/3 Mn 1/3 O 2 as an active material, 4 parts of acetylene black as a conductive material, and 3 parts of polyvinylidene fluoride as a binder were slurried into a current collector foil. It was coated with an applicator, dried at 120 ° C. for 10 minutes and then pressed.
　負極は、活物質として黒鉛９３部、導電材としてアセチレンブラック２部、および、バインダーとしてポリビニリデンフルオライド５部を用い、正極と同じ工程で作製した。 The negative electrode was prepared in the same process as the positive electrode, using 93 parts of graphite as an active material, 2 parts of acetylene black as a conductive material, and 5 parts of polyvinylidene fluoride as a binder.
　電解溶液は、溶媒として炭酸エチレンと炭酸ジエチルとを２３℃での体積比で１：１に混合した溶媒を用い、前記溶媒に、減圧下７０℃で１２時間乾燥したＬｉ・ＢＦ2（ＣＮ）2をアルゴン雰囲気下で１Ｍ（１規定、１ｍｏｌ／Ｌ）になるように溶解した溶液を用いた。 The electrolytic solution used was a solvent obtained by mixing ethylene carbonate and diethyl carbonate in a volume ratio of 1: 1 at 23 ° C. as a solvent, and Li · BF 2 (CN) dried at 70 ° C. for 12 hours under reduced pressure. 2 1M (1 defined, 1 mol / L) under an argon atmosphere using a solution such that.
　セパレータは、ポリエチレン製微多孔膜(厚さ２０μｍ、気孔率４０％）を用いた。 The separator used was a polyethylene microporous membrane (thickness 20 μm, porosity 40%).
　上記で作製した正極と負極とを３０ｘ５０ｍｍ2に打ち抜き、１７０℃にて１０時間それぞれ乾燥した後、セパレータを介して対向させアルミニウム製のラミネート内に挿入し電解液を注液、減圧含浸後、真空シールして電池性能評価用単層ラミネートセル（電池）を作製した。 The positive electrode and negative electrode prepared above were punched out to 30 × 50 mm 2 and dried at 170 ° C. for 10 hours, respectively, opposed to each other through a separator, inserted into an aluminum laminate, injected with an electrolytic solution, impregnated under reduced pressure, and then vacuumed A single-layer laminate cell (battery) for battery performance evaluation was produced by sealing.
　［比較例３］
　電解溶液として、キシダ化学株式会社より購入した電池研究用の、炭酸エチレンと炭酸ジエチルとを体積比で１：１に混合した溶媒に、ＬｉＰＦ6が１Ｍ（１規定、１ｍｏｌ／Ｌ）で溶解した電解溶液を用いた以外は、実施例３と同じ方法でセル（電池）を作製した。 [Comparative Example 3]
As an electrolytic solution, LiPF 6 was dissolved at 1 M (1 N, 1 mol / L) in a solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1 for battery research purchased from Kishida Chemical Co., Ltd. A cell (battery) was produced in the same manner as in Example 3 except that the electrolytic solution was used.
　《評価》
　＜初期充放電特性＞
　上記実施例３および比較例３で作製した単層ラミネートセル（電池）を、２．７Ｖから４．２Ｖの範囲で充放電を行い、３回目を初期充放電特性とした。初期充放電特性の測定結果を図３および表４に示す。 <Evaluation>
<Initial charge / discharge characteristics>
The single-layer laminate cell (battery) produced in Example 3 and Comparative Example 3 was charged and discharged in the range of 2.7 V to 4.2 V, and the initial charge / discharge characteristics were set for the third time. The measurement results of the initial charge / discharge characteristics are shown in FIG.
　＜高温保存性能＞
　上記実施例３および比較例３で作製した電池の初期充放電試験を行った後、抵抗を測定した。その後、８５℃にて１０日保存し、再度、抵抗を測定した。結果を表４に示した。 <High temperature storage performance>
After conducting the initial charge / discharge test of the batteries prepared in Example 3 and Comparative Example 3, the resistance was measured. Then, it preserve | saved for 10 days at 85 degreeC, and resistance was measured again. The results are shown in Table 4.
　＜低温動作性＞
　上記実施例３および比較例３で作製した電池の初期充放電試験を行った後、－３０℃にて、放電容量および抵抗を測定した。結果を表４に示す。 <Low temperature operability>
The batteries prepared in Example 3 and Comparative Example 3 were subjected to an initial charge / discharge test, and the discharge capacity and resistance were measured at −30 ° C. The results are shown in Table 4.
Figure JPOXMLDOC01-appb-T000004
 　表４に示した通り、初期充放電特性の評価結果より、実施例３で作製した電池は、常温において、比較例３で作成した電池と同等の初期充放電特性を示すこと分かった。
Figure JPOXMLDOC01-appb-T000004
 As shown in Table 4, it was found from the evaluation results of the initial charge / discharge characteristics that the battery produced in Example 3 exhibited the same initial charge / discharge characteristics as the battery produced in Comparative Example 3 at room temperature.
　また、高温保存性能の評価結果より、実施例３で作製した電池は、高温保存後（８５℃、１０日）において、比較例３で作製した電池と比べて抵抗の上昇が小さく、高温でより安定であることが分かった。 In addition, from the evaluation results of the high temperature storage performance, the battery produced in Example 3 has a small increase in resistance compared with the battery produced in Comparative Example 3 after high temperature storage (85 ° C., 10 days). It was found to be stable.
　さらに低温動作性の評価結果から、実施例３で作製した電池は比較例３で作製した電池と比較して、低温において放電容量が大きく、また、抵抗が小さいため、低温での電池性能に優れることが分かった。 Furthermore, from the evaluation results of the low temperature operability, the battery produced in Example 3 has a higher discharge capacity and lower resistance at a lower temperature than the battery produced in Comparative Example 3, and thus has superior battery performance at low temperatures. I understood that.

Claims (7)

  1. 　非水溶媒中に少なくとも１種のリチウム塩が溶解している非水電解液であって、
    　前記非水溶媒が、鎖状カーボネート、環状カーボネート、鎖状エステル、ラクトンおよびエーテルよりなる群から選ばれる少なくとも１種を含み、
    　前記リチウム塩が、下記一般式（Ｉ）で表されるシアノフルオロボレート・リチウム塩を少なくとも１種含み、
    Ｌｉ・ＢＦX（ＣＮ）4-X　　…（Ｉ）
    （Ｘは１～３の整数である）
    　非水電解液に含まれる全リチウム塩の合計の濃度が０．３～４ｍｏｌ／Ｌであることを特徴とする非水電解液。     A non-aqueous electrolyte in which at least one lithium salt is dissolved in a non-aqueous solvent,
    The non-aqueous solvent contains at least one selected from the group consisting of a chain carbonate, a cyclic carbonate, a chain ester, a lactone and an ether,
    The lithium salt contains at least one cyanofluoroborate lithium salt represented by the following general formula (I):
    Li · BF X (CN) 4-X (I)
    (X is an integer of 1 to 3)
    A nonaqueous electrolytic solution, wherein the total concentration of all lithium salts contained in the nonaqueous electrolytic solution is 0.3 to 4 mol / L.
  2. 　前記一般式（Ｉ）で表わされるシアノフルオロボレート・リチウム塩の合計の濃度が、０．３～４ｍｏｌ／Ｌであることを特徴とする請求項１に記載の非水電解液。 The non-aqueous electrolyte according to claim 1, wherein the total concentration of the cyanofluoroborate / lithium salt represented by the general formula (I) is 0.3 to 4 mol / L.
  3. 　前記非水溶媒が、鎖状カーボネートと環状カーボネートとを含むことを特徴とする請求項１または２に記載の非水電解液。 The non-aqueous electrolyte according to claim 1 or 2, wherein the non-aqueous solvent contains a chain carbonate and a cyclic carbonate.
  4. 　蓄電デバイスに用いられることを特徴とする請求項１～３のいずれか１項に記載の非水電解液。 The non-aqueous electrolyte according to any one of claims 1 to 3, wherein the non-aqueous electrolyte is used in an electricity storage device.
  5. 　リチウム電池、リチウムイオン電池またはリチウムイオンキャパシタに用いられることを特徴とする請求項１～３のいずれか１項に記載の非水電解液。 The nonaqueous electrolytic solution according to any one of claims 1 to 3, which is used for a lithium battery, a lithium ion battery, or a lithium ion capacitor.
  6. 　正極、負極および請求項１～５のいずれか１項に記載の非水電解液を有することを特徴とする蓄電デバイス。 An electricity storage device comprising a positive electrode, a negative electrode, and the non-aqueous electrolyte according to any one of claims 1 to 5.
  7. 　リチウム電池、リチウムイオン電池またはリチウムイオンキャパシタであることを特徴とする請求項６に記載の蓄電デバイス。 The power storage device according to claim 6, wherein the power storage device is a lithium battery, a lithium ion battery, or a lithium ion capacitor.
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